Application Implementations

Privacy

Secure communication over nonsecure networks involves two major areas of concern: privacy and authentication.

Using data encryption, an unencrypted (plaintext) message can be scrambled to appear like random characters . This message can consist of ASCII text, a database file, or any data that needs to be stored or transmitted securely. Encrypted text (cyphertext) is very difficult to translate back into the original message without a secret key.

Encryption and Decryption

Data encryption and decryption is a simple process. When a message is encrypted, an encryption key is used. This is comparable to a key that is used to lock a padlock. To decrypt the message, a decryption key must be used. The encryption and decryption keys are often, but not always, the same key.

Figure 11.3 The encryption and decryption process

It is important to keep the encryption keys safe and to transmit them securely to other users. However, the challenge is to restrict access to the decryption key properly, because anyone who possesses the key will be able to decrypt all messages that were encrypted with the corresponding encryption key.

Once a message has been encrypted, it can be stored on nonsecure media or transmitted over a nonsecure network. Later, the message can be decrypted into its original form.